The announcement helped trigger the resignation of his defense secretary, Jim Mattis, stunned allies and raised fears of a long-threatened Turkish military offensive against us -backed Kurdish forces in northern Syria.
According to the Syrian Observatory for Human Rights, the London-based group monitoring Syria's civil war, and the local Manbij Military Council, more than a dozen people were killed or wounded in the attack.
The assault comes as the U.S. has begun the process of withdrawing from Syria.
Roughly 2,000 American troops remain in Syria, where they have operated since intervening in 2014.
Turkey strongly opposes YPG's presence in Manbij and reached a deal with the U.S.in June to end the terrorist group's presence in the town and conduct joint patrols.
It was not the first time that forces of the US-led coalition were subjected to attacks in the area, although they have been rare.More news: Unai Emery Gives Update On Arsenal's Chase For Barcelona Star
Statements published by the Islamic State's unofficial news agency, Amaq, said the attacker used an explosives-laden vest to target coalition forces and that nine American troops were killed or injured.
By March 2017, the USA chose to send hundreds of American troops to Manbij to be a visible presence in the city, so as to prevent Turkish forces from attacking the Kurds and also keep Russian forces at bay.
Trump was informed that pockets of ISIS militants remained in the Euphrates River valley and that USA military had not yet eliminated all of their strongholds.
It was unclear whether the attack might influence Trump's decision to give more time for the USA withdrawal, a conflict he has become intolerant of and described as "sand and death".
When Trump announced his decision to pullout, it sent shockwaves through Washington and the rest of the world.
Last month, President Donald Trump announced that the United States would begin pulling out all its 2,000 troops from Syria because IS had been "defeated". "Will attack again from existing nearby base if it reforms".
"Trump wants to implement these safe regions through cooperation with Turkey". Thanks for reading! You can make a tax-deductible donation here.
Trump did not elaborate further, but urged Erdogan to create a 20-mile exclusion zone around Kurdish positions to guarantee the Kurds' safety.
"I would hope the President would look long at hard at where he's headed in Syria", Graham said.